The present invention relates to handbrakes for railway freight cars and, in particular, to a handbrake that is suitable for use with a single-cylinder, truck-mounted brake rigging.
There is presently known in the prior art a single-cylinder, truck-mounted brake rigging, as shown in U.S. Pat. Nos. 4,613,016 and 4,793,446, which has been designed for use with truss-type brake beams. In this respect, the braking force applied through the rigging acts on the respective brake beams at the beam midpoint where maximum resistance to bending forces is effective by reason of the beam strut arm transferring the load between the beam compression and tension members. Such a single-cylinder rigging, when combined with truss-type brake beams, is believed to offer maximum efficiency of operation at a relatively low cost.
An object of the present invention is to provide a low-cost handbrake capable of interacting with a brake rigging of the foregoing type, so that the handbrake force, as well as the pneumatic power brake force, is applied at the midpoint of the respective brake beams, without requiring any additional levers to transmit the handbrake force from one brake beam to the other.
Another object of the invention is to provide a single-lever handbrake mechanism capable of applying the desired handbrake force through the pneumatic brake rigging components without imparting any significant torque force on the brake beam and/or rigging components.
A still further object of the invention is to configure the handbrake lever so as to cause the handbrake lever ratio to change during operation in order to limit its range of travel and thereby prevent interference with the truck axle.
In achieving the foregoing objectives, there is provided a handbrake for a railway vehicle comprising first and second spaced-apart brake beams, first and second transfer levers pivotally-connected intermediate the ends thereof to a respective one of the first and second brake beams, first and second force-transmitting means interconnected between corresponding arms of said first and second transfer levers, the first force-transmitting means including a brake actuator that is operable in response to the supply of fluid pressure to increase the length of the first force-transmitting means, whereby the first transfer lever is rotated in a brake application direction to accordingly increase the spaced-apart distance between the first and second brake beams, a transfer link connected to the first transfer lever so as to be arcuately movable therewith in a plane parallel to the plane of rotation of the first transfer lever, a bearing surface on said first brake beam, and a handbrake lever having a pivotal connection at a location intermediate the ends thereof with the transfer link, one end of the transfer lever being adopted to receive a handbrake force and the other end of the handbrake lever being freely engageable with the bearing surface to provide a fulcrum about which the handbrake lever is rotatable.